1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to comminutors for treating solid material in a liquid waste stream containing solid waste.
2. Description of the Related Art
By definition, comminution is the reduction of particle size of solid waste material to minute particles. The comminution or the reduction of particle size of solid waste material into fine particles is performed by feeding solid waste material into the interface of counter-rotating intermeshed cutting elements while entrained in a liquid. These cutting elements may be in the form of a disk and may have projecting cutting teeth which overlap during rotation. The solids are then sheared and shredded by the action of the adjacent rotating elements, i.e., comminutors.
However, the cutter shafts of a dual shafted comminutor assembly tend to deflect away from each other when macerating heavy solids. If this deflection becomes excessive, the solids may not be completely ground. The deflection may also induce shaft failure, and if excessive enough, may damage adjacent components by direct contact.
In the related art as shown in FIG. 1, the counter-rotating cutter stacks 44 and 46 comprise an alternating sequence of cutting elements 48 and spacers 50 fitted over a shaft 5, 68. The overlap and counter-rotation occurring on zone 52 shreds the material as it passed through the cutter elements. The deflection of the cutter shafts may be limited by installing one or more floating intermediate shaft supports 10 along the cutter stacks 44, 46 which are held in place by the compression of the cutter stack elements allowing them to float as they operate. The downside to these intermediate shaft supports is that they wear unevenly due to side and axial loads that occur from macerating forces and gravity. The result is premature wear that typically requires part replacement before the cutter stack requires replacing. Over time, improvements made to the floating design include lubrication ports and improved bushing materials, but these improvements have only resulted in incremental improvements in wear life. Thus, there is a need to improve the wear characteristics of these floating intermediate shaft supports 10.
As shown in FIGS. 2A-3A, each intermediate shaft support 10, also known as a yoke, is a passive device used to prevent the deflection of dual-shafted comminutor cutter stacks 44, 46 while macerating. It is comprised of two housings 20 or brackets fastened together and contain four friction reducing bushings 30 and two rotating inner races 40. Two bushings 30 are press-fit into each of the two machined bores of each housing 20. The two inner races 40 are then installed in each bushing 30 of one housing 20 and are then enclosed by the second housing 20, which are fastened using bolts 60, for example, to create a contained intermediate shaft support 10. Each inner race 40 has a close clearance fit to the bushings 30 which allows the races to rotate freely. Each inner race 40 may have a profile so as to engage and rotate with the shape of the cutter shafts 5,68. In this embodiment, the shape of the cutter shafts is hexagonal. The inner races may have a hex-shaped profile as shown in FIG. 3A.
The inner races 40 operate similar to bearing inner races, except that the mode of rotation is by the fixed bushings as opposed to rolling bearing balls or rollers. One or more intermediate shaft supports 10 are installed on the two cutter shafts 5, 68 at strategic locations relative to the cutters and spacers, with each support yoke taking the place of approximately four cutters and spacers on each shaft. The brackets have lubrication ports to allow for external addition of lubrication once the components are assembled and installed.
While these intermediate shaft supports have conventionally been floating, in one application where the cutters are sandwiched between two adjacent walls, the intermediate shaft support 10 was formed with side wall portions 11 that were bolted to the two adjacent walls for the purposes of maintaining the position of the walls as shown in FIGS. 3B-3D.
FIGS. 9 and 10 shows a comminutor in the related art having a intermediate shaft support 10 installed on the cutter stacks 46 that are disposed between two rotating screens 48. As is evident from these figures, removal and maintenance of the intermediate shaft support 10 requires substantial time an effort as the comminutor must be disassembled to access the intermediate shaft support.
However, these intermediate shaft supports are prone to wear. As such, the comminutor assembly must be periodically taken out of service for maintenance. This maintenance may include merely shutting down the comminutor to lubricate the shaft support, but eventually, the comminutor assembly, including the two cutter shafts, must be disassembled to rebuild or replace the intermediate shaft supports.